An example of technique concerning a personal authentication system using a face image is disclosed in PTL 1. PTL 1 matches the face image of a person and performs matching using an eigenvector of a Fourier spectrum pattern which is made by performing Fourier analysis on an entire image. Then, it is possible to evaluate whether an input image is a specific person or not, and thus the input image can be used for personal authentication.
In PTL 1, by registering a face image of each person or feature extracted from the face image in advance, and comparing and matching the input face image and the registered face image or the feature extracted from the face image, it is possible to evaluate whether the input face image is the registered person or not, thereby enabling authentication of the person.
As other related arts, an example of an image recognition system that can perform correct categorization even when there is a concealment in the input image is described in PTL 2. PTL 2 obtains a matching result of a whole image after performing a matching process to each partial image of the input image, and especially since a matching score can be output that has a tendency of removing influence of the part including the concealment in an object to be matched, it can be also said as a matching technique using the part excluding the concealed part. It is needless to say that this technique can also be used for personal authentication applications by a face image.
Since the face image authentication system as above can generally use a non-contact sensor like a video camera as an input apparatus of an image, there is an advantage that it is not necessary for a person to be authenticated to contact the sensor.
On the other hand, generally the biometric authentication system including a face authentication system cannot completely zero an error rate in any authentication method. Therefore, in order to increase the accuracy of the authentication system, not only the biometric authentication but non-biometric authentication such as a password and an IC card may be combined and used. For example, PTL 3 discloses a hybrid personal authentication apparatus that combines face authentication, voice verification, a password, and an IC card.
Further, PTL 4 discloses a registration apparatus and a matching apparatus that include, in order to prevent leak of a pattern to be identified, a conceal processing unit that conceals all or a part of an object to be identified, a display control unit that displays an image in which all or a part of the object to be identified is concealed, so that a whole captured image will not be displayed on a screen.